In the construction of a radial ply tire, a carcass consisting of one or more preparation plies of elastomeric material is built up on a generally cylindrical drum. The preparation ply is applied so that reinforcing cords run from bead to bead in a direction that is generally parallel to the axis of the drum. Thus, prior to making the carcass, the preparation ply with the transversely extending reinforcing cords must first be made.
It is known to manufacture the preparation ply by first producing a sheet of elastomeric material in which reinforcing cords extend longitudinally. During production, the sheet of elastomeric material passes between calendering rolls. The calendered sheet of material is then cut into quadrilateral, for example, rectangular pieces, reoriented and the calendered edges are then spliced together to form a continuous strip of preparation ply material. The reorientation results in the reinforcing cords extending substantially parallel to the splice joints and substantially perpendicular to the longitudinal direction of the preparation ply strip.
If the elastomeric material has metallic reinforcing cords, the lateral calendered edges of the material have relatively straight and uniform edges. Thus, in the manufacture of a preparation ply that has metallic reinforcing cords, the adjacent ends of the strips are placed in direct opposition and brought together without any overlap of the ends to form an end-to-end or butt joint splicing the two ends together. Thus, the ends are held together only by the tackiness of the uncured rubber over the area of the adjacent ends. Metallic reinforcing cords provide a relatively linear calendered edge that is suitable for a butt splice bond created by the tackiness of the elastomeric material.
However, if the elastomeric material has nonmetallic reinforcing cords, the lateral calendered edges of the material are not straight but undulating. Such curved calendered edges provide a nonuniform and variable gap between the adjacent ends of the pieces and thus, are generally not considered suitable for a butt splice. Consequently, although a butt splice would be preferred in the manufacture of a preparation splice, an overlapping splice is often used to join the cut pieces having nonmetallic reinforcing cords.
Therefore, there is a need for improved apparatus and method for automatically making a preparation ply with butt splices. More particularly, there is a need for apparatus and methods for automatically butt splicing together a preparation ply having nonmetallic reinforcing cords.